Is it possible to run SSD or YOLO object detection on Raspberry Pi 3 for live object detection?
No.
YOLO and SSD are based on Nvidia's proprietary CUDA technology which is not available on Raspberry simply because of the GPU vendor is not Nvidia.
Even more, there seems to be no implementation of even OpenCL for the Raspberry's GPU.
What you can do is to try port YOLO's of SSD's CNN core from CUDA to Raspberry GPU's assembler, in the way described in, for example,  https://rpiplayground.wordpress.com/2014/05/03/hacking-the-gpu-for-fun-and-profit-pt-1/